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126 results on '"Speier, Gabor"'

22. New functional model complexes of intradiol-cleaving catechol dioxygenases: Properties and reactivity of [Cu.sup.II](L) ([O.sub.2]Ncat)

Author

Kaizer, Jozsef, Reglier, Marius, Zsigmond, Zoltan, Ganszky, Ildiko, Speier, Gabor, and Giorgi, Michel

Subjects
Catechin -- Structure, Catechin -- Chemical properties, Copper compounds -- Structure, Copper compounds -- Chemical properties, Glycols -- Structure, Glycols -- Chemical properties, Chemistry
Abstract

The complexes of copper and nitrocatechol dioxygenases are analyzed by x-ray crystallogrphy and various spectroscopies. The activity of catechol dioxygenase is proved.

Published
2007

27. Kinetics and mechanism of the base-catalyzed oxygenation of flavonol in DMSO-H (sub)2 O solution

Author

Balogh-Hergovigh, Eva and Speier, Gabor

Subjects
Chemistry, Organic -- Research, Oxygen -- Physiological aspects, Solution (Chemistry) -- Physiological aspects, Hydrogen -- Physiological aspects, Spectrophotometry -- Usage, Biological sciences, Chemistry
Abstract

Research has been conducted on the base-catalyzed flavonol oxygenation. The kinetics of this oxygenation has been investigated in the DMSO-H (sub)2 O solution using the spectrophotometric techniques and the results indicate that the reaction has shown specific base catalysis.

Published
2001

30. Preparation and oxygenation of (flavonolato) copper isoindoline complexes with relevance to quercetin dioxygenase

Author

Balogh-Hergovich, Eva, Kaizer, Jozsef, Speier, Gabor, Huttner, Gottfried, and Jacobi, Albrecht

Subjects
Crystals -- Structure, Crystals -- Atomic properties, Copper compounds -- Structure, Copper compounds -- Atomic properties, Copper compounds -- Chemical properties, Chemistry, Inorganic -- Research, Chemistry
Abstract

Copper(I) and copper(II) flavonolate complexes with the tridentate ligand isoindoline were prepared, oxygenated to copper o-benzoylsalicylate complexes and carbon monoxide, and used as catalysts for the oxygenations of flavonol in reactions that mimic the quercetinase enzyme reaction. The crystal structures of a copper(II) flavonolate complex with indH and that of (O-benzoylsalicylato)copper(I) complex are reported.

Published
2000

31. Kinetics and mechanism of the oxygenation of potassium flavonolate. evidence for an electron transfer mechanism

Author

Barhacs, Laszlo, Kaizer, Jozsef, and Speier, Gabor

Subjects
Mechanical chemistry -- Research, Chemical reaction, Rate of -- Analysis, Potassium salts -- Usage, Flavones -- Analysis, Organic compounds -- Synthesis, Biological sciences, Chemistry
Abstract

The mechanism of oxygenation of potassium flavonolates in dimethyl fluoride with reference to the formation of intermediates is investigated by electron paramagnetic resonance spectroscopy. Data suggest that the oxygenolysis of the flavonolate ion exhibits a single electron transfer mechanism, which eventually leads to the formation of O-benzoylsalicylate and carbon monoxide.

Published
2000

32. Quercetin 2,3-dioxygenase mimicking ring cleavage of the flavonolate ligand assisted by copper. Synthesis and characterization of copper(I) complexes (Cu(PPh3)2(fla)) (fla = flavonolate) and (Cu(PPh3)2(O-bs)) (O-bs = O-benzoylsalicylate)

Author

Balogh-Hergovich, Eva, Kaizer, Jozsef, Speier, Gabor, Fulop, Vilmos, and Parkanyi, Laszlo

Subjects
Copper compounds -- Research, Ligands (Biochemistry) -- Research, Metalloenzymes -- Research, Quercetin -- Research, Ring formation (Chemistry) -- Research, Tetrahydrofuran -- Usage, Chemistry
Abstract

Research was conducted to examine in detail the synthesis and characterization of (Cu(PPh3)2(fla)) (fla = flavonolate) and (Cu(PPh3)2(O-bs)) (O-bs = O-benzoylsalicylate). The crystallographic characterization of the complex has demonstrated that the coordination geometry of the molecule is tetrahedral. The details of the oxidative ring cleavage reaction supported by 18O-labeling and kinetic experiments are also reported.

Published
1999

36. Studies on aerobic reactions of ammonia/3,5-di-tert-butycatechol Schiff-base condensation products with copper, copper(I) and copper(II). Strong copper(II) - radical ferromagnetic exchange and obsertvations on a unique N-N coupling reaction

Author

Speier, Gabor, Csihony, Jozsef, Whalen, Anne M., and Pierpont, Cortlandt G.

Subjects
Copper compounds -- Analysis, Ammonia -- Analysis, Ferromagnetism -- Analysis, Amines -- Analysis, Chemistry
Abstract

The presence of copper enhances the selectivity and direction to the amine condensation process of the oxidation chemistry of trihydroxyphenylalanine models. The three synthetic reaction series of Cu(II), Cu(I) and Cu(0) produces Cu(py)2(Cat-N-SQ) as a major product. The oxidative dimerization of iminosemiquinone ligands at the metal ion forms azenophenolates that are bound to Cu in Cu(py). The Cu(Cat-N-SQ) subunits play a major role in the synthesis of extended polymers with cooperative ferromagnetic properties. N-N bonds are detected after the condensation of trihydroxyphenylalanine.

Published
1996

39. Iminosemiquinone complexes of copper: structural, magnetic, and electrochemical characterization of complexes of the phenoxazinolate semiquinone radical

Author

Speier, Gabor, Whalen, Anne M., Csihony, Jozsef, and Pierpont, Cortlandt G.

Subjects
Copper compounds -- Research, Quinone -- Research, Molecular structure -- Research, Ferromagnetism -- Analysis, Chemistry
Abstract

Spectroscopic and crystallographic studies of iminosemiquinone complexes of copper indicate that the complexes possess a tetrahedral geometry and that the iminoquinone ligands undergo one-electron oxidation and reduction reactions. An S=1/2 magnetic ground state is observed in the complexes at low temperatures. A ferromagnetic exchange takes place between the phenoxazinolate semiquinone (PhenoxSQ) ligands, while an antiferromagnetic exchange occurs between copper and PhenoxSQ.

Published
1995

41. Coligand-dependent shifts in charge-distribution for copper complexes containing 3,5-Di-tert-butylcatecholate and 3,5-Di-tert-butylsemiquinonate ligands

Author

Speier, Gabor, Tisza, Sandor, Tyeklar, Zoltan, Lange, Christopher W., and Pierpont, Cortlandt G.

Subjects
Copper compounds -- Research, Metal ions -- Research, Charge transfer -- Analysis, Chemistry
Abstract

Reaction between copper metal and 3,5-di-tert-butyl-1,2-benzoquinone (3, 5-DBBQ) results in the formation of Cu(py)2(3,5-DBCat) and characterization is done in the presence of triphenylphosphte monomeric units attached at basal centers by connecting catecholate oxygen atoms. Charge distribution is controlled by coligand banding effects and quinone ligands and is sensitive to the orbital energy of the metal ion.

Published
1994

42. Synthesis and characterization of (tetramethylethylenediamine)(9, 10-phenanthrenequinone)(9,10-phenanthrenediolato)copper(II), a copper complex containing mixed-charge 9,10-phenanthrenequinone ligands

Author

Speier, Gabor, Tisza, Sandor, Rockenbauer, Antal, Boone, Steven R., and Pierpont, Cortlandt G.

Subjects
Catecholamines -- Research, Copper -- Research, Chemistry
Abstract

The compound (tetramethylethylenediamine)(9,10-phenanthrenequinone) (9, 10-phenanthrenediolato)copper(II), Cu(TMEDA)(PhenCat)(PhenBQ), was prepared by refluxing a solution of copper wire, 9,10-phenanthrenequinone and tetramethylethylenediamine. The Cu(TMEDA)(PhenCat)(PhenBQ) molecule shows a square pyramidal coordination geometry with basal sites determined by the TMEDA and phenanthrenediolate ligands. The 9,10-phenanthrenequinone ligand is bonded to the metal at the apex through one oxygen atom. Crystals of the complex form in the monoclinic crystal system, space group P2(sub 1)/n.

Published
1992

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